Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753795AbZDMS2A (ORCPT ); Mon, 13 Apr 2009 14:28:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752243AbZDMS1u (ORCPT ); Mon, 13 Apr 2009 14:27:50 -0400 Received: from smtp.ultrahosting.com ([74.213.174.254]:58577 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752139AbZDMS1u (ORCPT ); Mon, 13 Apr 2009 14:27:50 -0400 Date: Mon, 13 Apr 2009 14:18:08 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@qirst.com To: Ingo Molnar cc: Linus Torvalds , Tejun Heo , Martin Schwidefsky , rusty@rustcorp.com.au, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, Paul Mundt , rmk@arm.linux.org.uk, starvik@axis.com, ralf@linux-mips.org, davem@davemloft.net, cooloney@kernel.org, kyle@mcmartin.ca, matthew@wil.cx, grundler@parisc-linux.org, takata@linux-m32r.org, benh@kernel.crashing.org, rth@twiddle.net, ink@jurassic.park.msu.ru, heiko.carstens@de.ibm.com, Nick Piggin , Peter Zijlstra Subject: Re: [PATCH UPDATED] percpu: use dynamic percpu allocator as the default percpu allocator In-Reply-To: <20090408162651.GA14449@elte.hu> Message-ID: References: <49D2B209.9060000@kernel.org> <20090401154913.GA31435@elte.hu> <20090401190113.GA734@elte.hu> <20090401223241.GA28168@elte.hu> <20090402034223.GA25791@elte.hu> <20090408162651.GA14449@elte.hu> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2041 Lines: 47 On Wed, 8 Apr 2009, Ingo Molnar wrote: > Dude, this is a new facility freshly modernized and freshly made > usable. What did you expect, for a thousand usecases pop up in the > kernel overnight? _None_ of this code is "common" today per se. (the > networking folks are working on making it more and more common > though) ?? kfree(NULL) has been allowed for years. None of this is new. > > Speculation. A shutdown fastpath? The percpu allocation and free > > operations are expensive and deal with teardown and setup of > > virtual mappings. Those paths are *not* optimized for fastpath > > use. kfree is different. > > Of course a lot of this is speculation, dynamic percpu so far has > been a rarely used facility compared to kmalloc()/kfree(). If you > dont accept my analogy that's fine - but that is opinion against > opinion - while you state you opinion as truism. Please look at the kernel source for the use of percpu_free and percpu_alloc. > So my point remains: your patch had effects you clearly did not > anticipate, and the cacheline alignment management situation is not > nearly as clear-cut as you imagine it to be. There was no effect that I did not anticipate. Just imagination on your part that percpu_free is used like kfree. Again: The frequent insertion of __read_mostly will destroy the purpose and function of the read mostly areas! > Unfortunately you failed to answer my detailed mail that made very > specific points though, you only got into generalities and flames > about my summary mail - so it's hard to judge what your opinion > about those specific facts is - you have not stated one. I was pretty clear on those points. Not sure what material question I did not answer. What you say here fits your posts. Generalizing from kfree to percpu_free etc... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/